A new methodological principle permitting clonal analyses of lymphoid cells is being applied to investigate the dynamics of B cell activation and to improve the diagnosis of the human immunodeficiency viruses (HIV). Based on the enzyme-linked immunospot (ELISPOT) assays, co-discovered by a member of our group, these methods allow quantitative assessments, in the blood and other body fluids or tissues, of B cells secreting immunoglobulins (IG's) of different isotypes to specific antigens. Single cells releasing immunoreactive substances, such as viral antigens, can also be enumerated. These methods should circumvent several difficulties associated with HIV diagnosis, e.g. transplacentally- acquired antibodies in infants, or problems in defining immune responses with other assays, e.g. the possible effects of immune complexes or of competition between Ig isotypes for HIV antigens. We propose to apply the ELISPOT methodology in longitudinal studies of the offspring of HIV antibody positive pregnant women (routine prenatal testing in our hospital with 10,000 pregnant women a year indicates that already over 0.5% are HIV antibody positive). Together with the use of other virological (including polymerase chain reaction assays) and more conventional immunological tests, the information obtained would be particularly valuable in defining truly infected infants for therapeutic trials, in furthering our understanding of the immunobiology of the HIV- infected and non-infected infants, and in delineating the immunobiology of the HIV-infected adults and infants, providing support for the possibility of detecting and enumerating HIV antibody-secreting lymphocytes to specific viral proteins. Similarly, we have developed the methodology for the enumeration of immunoglobulin secreting cells of different isotypes in children and adults which should permit the B cell clonal proliferation so prominent in HIV-infected individuals, particularly children, to be monitored. Studies will also be performed to enumerate mononuclear cells (and subsets) releasing HIV antigens. The methodologies developed should provide important diagnostic and prognostic markers for current and eventual prevention (e.g. vaccine) or therapeutic (e.g. antiviral and immune modulator) interventions for HIV infection in individuals of all ages.